1. Field of the Invention
The invention relates to a sputtering apparatus, and particularly relates to a sputtering apparatus suitable for stabilizing and improving film quality of a thin film deposited on a substrate. More particularly, it relates to an improvement of a process chamber of a sputtering apparatus in which a thin film is deposited on an upwardly facing substrate.
2. Description of the Related Art
Referring to FIGS. 7 and 8, examples of a process chamber in a conventional sputtering apparatus will be explained below.
FIG. 7 shows a first example of a conventional sputtering apparatus. This sputtering apparatus has both a face-down orientation means and a side-sputtering orientation means. The orientation of the substrate is such as to make its surface to be processed (hereinafter referred to as "processing surface") face downward or sideways. This orientation prevents dust particles from falling down on the processing surface of the substrate, thereby reducing the contamination by the dust particles of the processing surface. Here, the face-down orientation means is defined as one in which the orientation of the substrate is horizontal so as to make the processing surface of the substrate face downwardly. On the other hand, the side-sputtering orientation means is defined as one which orients the substrate vertically so as to make the processing surface face sideways during a sputtering process.
In FIG. 7, the first conventional sputtering apparatus includes a process chamber 51, a target 52 arranged in a vertically oriented manner, a target holding member 53, a ring-like target shield member 54, a substrate 55, a substrate holder 56 for mounting the substrate 55, a substantially cylindrical substrate holder shield member 57, and a cylindrical shield member 58. When depositing a thin film on the processing surface of the substrate 55, the substrate holder 56 is vertically oriented as shown by the solid line in FIG. 7. In this case, the surface of the substrate holder 56 is opposite the surface of the target 52. A plasma discharge 59 is generated between the substrate 55 and the target 52 to thereby perform thin film deposition. When transferring the substrate 55, the substrate holder 56 is horizontally oriented as shown by the broken line in FIG. 7. In this case, the processing surface of the substrate 55 faces downward. The substrate 55 is transferred in this orientation by means of a transfer means (not shown). Therefore, the substrate holder 56 can be turned as shown by an arrow 60, by means of an orienting means (not shown). As a result, the orientation of the substrate 55 on the substrate holder 56 is also changed. According to the face-down orientation, the dust particles can be prevented from falling down onto the processing surface because it faces downward during substrate transfer. According to the side-sputtering orientation, on the other hand, the dust particles fall down in the space between the substrate and the target by the action of gravity during the thin film deposition process. Accordingly, the influence of contamination by the dust particles of the processing surface of the substrate can be reduced. In FIG. 7, the first conventional sputtering apparatus further includes a gas inlet means 61 for introducing a process gas 62 into the process chamber 51, and another shield member 63.
The first conventional sputtering apparatus must have a transfer means for the face-down orientation and a thin film depositing means available for the sidesputtering orientation. Accordingly, the apparatus has a disadvantage that the transfer means becomes complicated and the volume of the process chamber becomes inevitably large. Further, the shield members are provided, at places where there is a possibility of deposition of the thin film, for the purpose of preventing the thin film from depositing on undesired portions such as the side surface of the substrate holder 56. The number of the shield members becomes relatively large and therefore the number of maintenance items increases. The apparatus has a further disadvantage that the pump-down time becomes long because the volume of the process chamber is large.
FIG. 8 is a vertical section showing a second example of the conventional sputtering apparatus. The sputtering apparatus has a face-up orientation means in which the processing surface of a substrate faces upward during the substrate transfer and during the thin film deposition because the amount of the dust particles generated is reduced due to a technical improvement. In FIG. 8, elements substantially the same as those in FIG. 7 are referenced correspondingly. In FIG. 8, in the process chamber 51 of the apparatus, the orientation of the substrate 55 does not change. Further, the process chamber 51 is provided with two gas inlet lines 61A,61B for each gas 62A,62B to flow, as shown by the broken line arrows, and a vacuum gauge 65 for measuring the pressure in the process chamber 51.
In the second conventional sputtering apparatus, since the orientation of the substrate is not changed in the process chamber 51, the volume of the process chamber 51 and the surface area thereof can be made small. As a result, the second conventional sputtering apparatus has an advantage that the pump-down time is shortened, and the shield configuration is integrally formed to thereby reduce the number of the shield members. Therefore the maintenance time can be shortened. Thus, the problems pointed out in the foregoing first conventional sputtering apparatus can be solved.
The second conventional sputtering apparatus, however, has a disadvantage in that the process gas cannot be sufficiently introduced to the plasma discharge space 59 because the space is substantially tightly enclosed by the cylindrical shield member 58, and because the locations of the gas inlet lines are limited because of the mechanical structure to the side wall of the process chamber and the substrate holder. Further, since the vacuum gauge 65 must be attached to the side walls of the process chamber because of the mechanical structure, the pressure in the plasma discharge space 59 cannot be accurately measured.